The present invention relates to a catalyst for producing liquid hydrocarbons from paraffinic hydrocarbons in the presence of hydrogen and a process for producing liquid hydrocarbons using such a catalyst.
In recent years, demands have been escalating rapidly toward a clean liquid fuel which is low in contents of sulfur and aromatic hydrocarbons. In response to such demands, fuel oil manufacturers have already been studying various processes for producing clean fuel. Among these, a process has been considered to be the most prospective in which process paraffinic hydrocarbons such as waxes are hydrocracked in the presence of a catalyst.
In a process of hydrocracking of a paraffinic hydrocarbon, it is important to produce useful middle distillates at higher yields in order to improve the economical efficiency of the process. In addition, the resulting gas oil is necessarily low in pour point. That is, development of a highly efficient hydrocracking catalyst which can enhance the cracking activity and middle distillate yield of the hydrocracking process and can render the process possible to produce a gas oil with low pour point holds the key to an improvement of economical efficiency of the process.
Hydrocracking of a vacuum gas oil has already been commercialized and is a technology which has been established for more than decades. However, since the difference between the reactivity of a paraffinic hydrocarbon and that of a vacuum gas oil is so significant that it is difficult to use the catalyst for the latter as it is for hydrocracking a paraffinic hydrocarbon, the research and development have been continued vigorously to aim development of a highly efficient catalyst for paraffinic hydrocarbons. There are a few but some patents and reports concerning such a catalyst. For example, Patent Document 1 below discloses a catalyst comprising platinum loaded into a support containing silica alumina. There is an example of a study in Non-Patent Document 1 wherein the hydrocracking of a paraffinic hydrocarbon was carried out using a catalyst comprising platinum loaded into a crystalline aluminosilicate (zeolite).
However, the crystalline aluminosilicate catalyst is at a satisfactorily higher level of the cracking activity but has disadvantages that the middle distillate yield is low and the resulting gas oil fails to obtain a sufficient pour point. On the other hand, amorphous solid acid catalysts a typical example of which is silica alumina are at satisfactorily higher level in middle distillate yield and the pour point of the resulting gas oil but low in cracking activity. That is, there has not been developed a catalyst which satisfies high cracking activity and middle distillate yield as well as the low pour point of the resulting gas oil all together, resulting in a serious hindrance to an improvement of economical efficiency of the hydrocracking process of paraffinic hydrocarbons.
(1) Patent Document 1: Japanese Patent Laid-Open Publication No. 6-41549
(2) Non-Patent Document 2: “Zeolite” (Volume 6, page 334 to 348, 1986)